Heretofore, as a process for preparing pyran-4-one, there have been known, for example, a method in which 4-methoxy-3-buten-2-one and methyl formate are reacted in ether in the presence of sodium methoxide to precipitate a sodium salt of a formyl derivative, then, a methanol solution of hydrogen chloride is reacted thereto, neutralized and distilled under reduced pressure to give a mixture containing 1,5,5-trimethoxy-1-penten-3-one as a main component, further, the mixture is allowed to stand in conc. hydrochloric acid overnight, then neutralized and extracted to prepare pyran-4-one (for example, see Patent literature 1). However, according to this method, a sodium salt of a formyl derivative which is an intermediate must be once precipitated, and, a methanol solution of hydrogen chloride which is difficult to handling must be used, a reaction operation is complicated and a reaction time is extremely long, so that it is not advantageous as an industrial process for preparing pyran-4-one.
Moreover, as a process for preparing tetrahydropyran-4-one from pyran-4-one, there has been disclosed, for example, a method in which pyran-4-one and hydrogen are reacted in the presence of Raney nickel, under normal pressure in ethanol at room temperature for 3 hours to prepare tetrahydropyran-4-one with yield of 58% (for example, see Non-Patent literature 1) or a method in which pyran-4-one and hydrogen are reacted in the presence of palladium/scandium carbonate under pressure in methanol at 20° C. for 30 minutes to prepare tetrahydropyran-4-one with yield of 75% (for example, see Non-Patent literature 2).
However, in the processes for preparing pyran-4-one, there are problems that a sodium salt of a formyl derivative which is an intermediate must be once precipitated, and, a methanol solution of hydrogen chloride which is difficult to handling must be used, a reaction operation is complicated and a reaction time is extremely long, and in a method for preparing tetrahydropyran-4-one from pyran-4-one, minute operation such as adjustment of catalyst activity shall be carried out to improve yield of the objective compound, so that it is not advantageous as an industrial process for preparing tetrahydropyran-4-one.
[Patent literature 1] Japanese Patent Publication No. Sho. 47-29512
[Non-Patent literature 1] Bulletin de la Societe Chimique de France, 1959, 36.
[Non-Patent literature 2] Helv. Chim. Acta., 31, 65(1948)